Gynecological brachytherapy applicator and system

ABSTRACT

A vaginal brachytherapy applicator is versatile to different anatomies and more comfortable to the patient than prior applicators. An inflatable balloon on a shaft may be inelastic or elastic. In one embodiment the shaft is rotatable relative to the balloon for enabling a ring or band of dose delivery, for versatility in radiation placement. Alternatively, the source can be rotated and pulled back within a stationary shaft. An adjustment is provided for reducing the length of balloon that inflates, to accommodate different anatomies and positions. Although isotope radiation sources can be used in the applicator, an electronic source is preferred, and the system and method include procedures for using the applicator with an electronic source.

This application is a continuation-in-part of application Ser. No.10/464,140, filed Jun. 18, 2003.

BACKGROUND OF THE INVENTION

This invention concerns radiation therapy, especially for treatingtissue which may have malignancies, and in particular the inventionrelates to an applicator for delivering radiation to a vaginal cavityand/or to adjacent tissue post full/partial hysterectomy for surgicaltreatment of cancer. Treatment of endometrial cancer is encompassed bythe invention.

Vaginal or endometrial cancer, or malignancies in adjacent tissues, havebeen treated by applicator cylinders designed to receive radioactiveisotopes. Applicators of this general type are shown, for example, inU.S. Pat. Nos. 5,913,813 and 6,413,204. Even though the applicatorcylinders are sized to the vaginal cavity or adjacent anatomy, thesetypes of applicators have often been uncomfortable or painful oninsertion and once inserted have failed to provide a good fit. Ideally,the tissue should be positioned closely against the applicator. Theconventional applicator can cause discomfort, inconvenience and lessthan ideal treatment in many cases. Such devices also lack flexibilityin dose delivery profile. Basically, prior art applicator cylinders haveincluded a straight lumen down the center through which radioactiveseeds were delivered.

SUMMARY OF THE INVENTION

The invention is an improved applicator for gynecological brachytherapy,more comfortable to the patient on insertion and in use, more versatile,and optimally with capability of rotating a radiation emitting device toproduce a ring or band of irradiated tissue. The device has a main shaftto which is secured or connected an inflatable balloon surrounding thedistal end of the shaft which will be inserted into the body of thepatient. The shaft may have alternate configurations for variations inpositioning a radiation source, or to accommodate a range of therapeutictreatments. Multiple guides for the radiation source(s) can be included,as also disclosed in copending application Ser. No. 10/464,140,incorporated fully herein by reference. The invention encompasses use ofisotopes, but especially in preferred embodiments, embraces applicationof variable voltage and/or current to a switchable electronic miniaturex-ray source (or to several sources) in order to optimize a treatmentplan. Also, the system can employ feedback control in real time, to feedactual sensor-determined radiation values back to a controller to adjustand control the dose delivered by the electronic radiation device, toachieve a desired dose profile even in a cavity of irregular shape,utilizing directionality of radiation if necessary.

In one preferred implementation of the invention, a brachytherapyapplicator comprises an inflatable balloon, with a shaft extending intothe interior of the balloon, the shaft having a conduit for inflatingthe balloon by admitting fluid to the balloon's interior. A source ofionizing radiation for delivery of radiation is affixed to or retainedat the distal end of a flexible catheter or a rigid wand, depending onthe application at hand. The source catheter or wand is contained in orreceived in the applicator shaft and is guided into the space within theballoon. A fluid tight seal, such as by a bonded joint, is provided atthe proximal end of the balloon to seal the balloon against the exteriorof the shaft in this embodiment. At the interior of the proximal end ofthe shaft in this preferred embodiment, an O-ring seal seals the shaftto the exterior of the flexible catheter or rigid wand comprising theradiation source, permitting rotation as well as axial movement betweenthe radiation source structure and the shaft without substantial fluidleakage.

The radiation source may be omni directional or direction specific tosuit the application. In one embodiment a radio opaque source guideincluding a radiation window is provided between the shaft and thesource catheter or wand to control the directionality of emittedradiation. The radiation source and source guide can be rotatable withinthe shaft without substantial loss of fluid from the interior of theballoon. A preferred form of the shaft is configured to allow pullbackof the radiation source.

In use, the balloon on the shaft is placed in a gynecological cavitywith the balloon deflated, the radiation source is inserted, and once inplace, the balloon is inflated (in some embodiments the balloon can beput in place and inflated before the radiation source is inserted). Withthe ionizing radiation source in the shaft, the source can be rotatedand/or moved axially by machine or by hand, manipulated from a positionoutside the patient to control the locations from which the radiation isto be emitted, and the directions in which the radiation is to bedirected.

In the various applicator embodiments described, the distal end of theapplicator shaft is preferably affixed to the distal end of the balloon,or includes a rotary bearing connecting the distal end of the shaft tothe distal end of the balloon, so as to permit rotation while supportingthe balloon on the shaft.

The distal end of the shaft or source guide (most remote from thecontroller as used herein) in one embodiment is bent to an oblique anglefor emitting the directional radiation outwardly and axially from theapplicator, with capability of rotating the shaft relative to theballoon; alternatively, directional radiation can be emitted from astraight shaft located generally centrally. The shaft of an applicatorrefers to that element of the applicator that connects to the balloon(rotationally or not) and which provides an internal lumen or guide forreceiving the radiation source.

Another preferred feature of the invention is a means for adjusting thesize of the inflated portion of the balloon. This can be accomplishedusing a slidable tubular sheath over the shaft that slides axiallyrelative to the shaft, and when moved forward (distally), covers adesired portion of the balloon from the proximal end of the balloon soas to prevent or limit expansion of the balloon in the sheath-coveredportion. The expanded length of the balloon is thus limited as desired.This adjustment accommodates different anatomies of different patients,as well as adjusts for different regions within the anatomy.

As noted above, the source of ionizing radiation in a particularpreferred embodiment is an electronic switchable x-ray source, which isnot only switchable on/off but is adjustable as to voltage and current,and thus as to x-ray penetration depth and cumulative dose delivered.This affords attaining a much more accurate delivered dose profile thancan be obtained using prior art methods since the control of radiationallows accommodation of differences in distance from source to tissueand differences in dose delivered to different tissue regions. It alsoprovides a more flexible and anatomy-conforming applicator.

When the anatomy demands, or when the morbidity requires, an embodimentis provided in which the shaft and other elements of the apparatus canbe bent to facilitate entry into the uterus after dilation. For example,the shaft may be formed in a continuous curve, or may comprise adeformable element, for example annealed metal, which may be formed bythe doctor to accommodate the patient's anatomy.

It is thus among the objects of the invention to greatly improveefficiency, reliability, versatility, patient comfort and dose accuracyin brachytherapy radiation within the vaginal cavity and adjacentanatomy. These and other objects, advantages and features of theinvention will be apparent from the following description of preferredembodiments, considered along with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view in cross-section of a preferred embodiment of theinvention.

FIG. 2 is a side view in cross-section of an applicator of theinvention, including a slidable tubular sheath covering a portion of theexpandable balloon, limiting its expansion.

FIG. 3 is a side elevation view of a curved embodiment of the applicatorsimilar to that of FIG. 1, in partial cross section.

FIG. 4 a is a side elevation view of a radio opaque outer element of asource guide with a window through which radiation may be directed.

FIG. 4 b is a side elevation view of the inner element of a radio-opaquesource guide with a window through which radiation may be emitted.

FIG. 4 c illustrates how the source guide elements can be assembled andhow the window depicted in FIGS. 4 a and 4 b may be adjusted tocooperate in obtaining a desired window through which a controlled beamof radiation is to emitted.

FIG. 5 depicts a side view of an alternate embodiment of the inventionin partial cross-section, comprising a shaft with a curved channel todirect radiation distally and rotatably about the shaft axis.

FIG. 5 a is a side view of an alternative bearing configuration inpartial cross section.

FIG. 5 b is a view similar to FIG. 5 but showing another embodiment.

FIG. 6 shows a side view in cross-section of apparatus of the inventioncomprising suction applied to the distal end of the applicator to drawof accumulated fluid or exudate.

FIG. 7 shows a portion of a patient's vaginal anatomy in coronal sectionwith early stage cancer (shaded) at the mouth of the cervix. Anapplicator of the invention positioned within the vagina.

FIG. 8 a shows the patient's anatomy with advanced cancer in coronalsection with an applicator of the invention positioned within the vaginaand partially into the uterus.

FIG. 8 b shows the anatomy of FIG. 8 a in medial sagittal section, againwith an applicator within the vagina and a portion of the uterus.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 depicts a basic embodiment of the invention. A radiation sourcecatheter or wand 100 has a radiation source 101 at its distal end. Thecatheter or wand 100 is shown assembled within a shaft 200. The shaft200 comprises a tubular body with a balloon 300 at its distal end 205.The distal end of the shaft 200 is bonded to the balloon at its distalextremity, and bonded to the balloon proximal extremity at 206.

At the proximal end 207 of the shaft 200 is a conventional applicatorhub (not shown) as is common in radiation applicators, including a port201 for balloon inflation fluid in communication with a fluid outlet 202within the balloon, and a seal receptacle 203 for an O-ring 204. TheO-ring 204 maintains a movable seal between the shaft 200 and thecatheter 100 in this embodiment, allowing both rotation and translationof the catheter within the shaft without loss of balloon inflationpressure.

FIG. 2 shows an optional tubular sheath 210 placed over and coaxial withthe shaft 200 and proximal end of the balloon 300.

The sheath 210 may be adjusted and positioned axially as desired alongthe body of the shaft 200 in order to limit the inflated length of theballoon. The sheath 210 can be held in position by a nut 211 and atapered thread 212 at the split, proximal end of the sheath 210. Whenpositioned as desired, the sheath 210 and nut 211 are rotated relativeto one another such that the tapered thread causes the split end of thesheath to tighten onto the shaft 200. The sheath may be rigid and ofmetal (stainless steel, for example) or engineering plastic and flexible(PVC, Nylon). Advantageously, it may be radio-opaque (e.g. barium loadedif plastic). In an alternate embodiment (not shown) a latch can beprovided on the sheath to engage with an element of the shaft or of ahub to position the sheath relative to the shaft.

The balloon 300 can be either elastic or inelastic in nature; that is,it can be of material to substantially conform to tissue, or material toform a generally rigid predefined shape. In use, the balloon preferablyabuts the patient's tissue to be treated. If the nature of the cavitybeing irradiated is irregular or rigid, an elastic construction isusually preferred. A suitable material is silicone rubber, and of such athickness that inflation pressure will cause expansion of the balloon tosubstantially fill the irregular cavity to be irradiated. If incontrast, the cavity to be irradiated is of fairly uniform geometry, orif the tissue is highly compliant, then an inelastic balloon might bepreferred. Such a balloon, constructed for example of PET orpolyurethane, can be fabricated to expand to a predetermined shape, andif properly proportioned, usually can deform the tissues to be treatedsuch that they conform to the balloon geometry. A balloon that assumes aknown (fairly rigid) shape has been important in use of isotoperadiation, with the isotope source positioned centrally in the balloonto produce a known distance to tissue and uniform dose distribution.Such is one embodiment of this invention, and can be considered asrepresented in FIGS. 1 and 2, and also in FIGS. 3, 6 a-6 b, 7 and 8 a-8b. With a controllable electronic x-ray source, however, more latitudeis permitted and irregular shapes can be treated, with conformingballoons.

Generally, it is preferable that the position of the radiation sourcewithin the balloon be known as precisely as possible. Therefore, it isusually advantageous that the balloon 300 be secured to or supported onthe shaft of the applicator at both distal and proximal balloonextremities. There may be situations, however, where the geometry of theanatomy to be treated and that of the balloon are sufficientlypredictable that anchoring of the balloon to the shaft only at theproximal end of the balloon is adequate for proper control of therapy.

Depending on the anatomy being treated, and perhaps its surroundinganatomy, it may be preferred that the applicator be curved as shown inFIG. 3. As shown the body of the shaft 301 has a continuous curve,although the form can be arbitrary to suit the anatomy of the patient.If desired, the body of the shaft 301 can be of deformable material suchas annealed stainless steel, and bent to suit by the radiationtherapist. Further, it could be of Nitinol according to the catheterteachings of U.S. Pat. No. 4,665,906. Use of a flexible source catheter100 permits the radiation source to be positioned at will along thetubular bore of the shaft 301. A situation in which a curved applicatoris preferred is shown in FIG. 8 b and discussed below.

The preferred radiation source of this invention is a miniature x-raytube 101, positioned at the end of a cable catheter or wand 100. Anexample of such an x-ray source is described in U.S. Pat. No. 6,319,188.Generally, they consist of a flexible, high-voltage cable (as part ofthe catheter 100) connected to a power source and controller at itsproximal end and to the small x-ray tube at its distal end. The x-raytube has a cathode which can be caused to emit electrons (for example byheat) at its proximal end and a target anode at its distal end. Thevoltage between the cathode and electrode accelerates the electronsemitted by the cathode such that they impact the anode creating x-rays.The spectrum of energies produced is related to the voltage appliedbetween the anode and cathode and the target material used. It is thisanode to cathode high voltage (as well as current control) that providesthe option for control of the radiation emitted from such an x-raydevice as compared to a radio-isotope source which always emits in aknown and unchangeable manner.

The shape of the anode, and its structure and shielding, determine thedirectionality of the x-rays emitted. They may be omni directional, orthey may be directed radially or axially, or a combination thereof.Anode shaping is well known by those skilled in the art of x-raygeneration apparatus. The penetration of the x-rays in tissue isdirectly related to the voltage accelerating the electrons, and thecumulative dose may be controlled by x-ray source beam current or dwelltime at positions within the body of the patient. Current can be variedin the tube to control cathode emission. It should also be noted thatdosimeters can be placed on the balloon at plural locations, thus to bedirectly adjacent to the tissue, and can sense dose from the source sothat the dose being delivered to different tissue regions being treatedis known. This enables control of dose delivered to all regions in anirregularly-shaped cavity and balloon; feedback control is disclosed incopending application Ser. No. 10/464,140, incorporated herein byreference.

On occasion, it is preferable to shape the emission field of the x-raytube by shielding the output of the source 101 rather than by anodedesign. An example of such shielding is illustrated by a directionalsource guide 400 in FIGS. 4 a-c. The directional source guide 400 isinside the lumen of an applicator shaft. FIG. 4 a shows in sideelevation the outer, tubular, radio opaque shield sleeve 401 having oneclosed end and a window 402 which is open for an arbitrary length and anarc B. FIG. 4 b shows an inner, tubular, radio-opaque sleeve 403 havingone closed end and a window 404 which is open for an arbitrary lengthand an arc A. The inner bore of the shield sleeve 401 accommodates theouter diameter of sleeve 403. The outer diameter of the sleeve 401 isaccommodated by the inner diameter of the shaft 200 and the O-ring seal204, if the applicator is constructed as in FIG. 1. The inner bore ofthe smaller sleeve 403 accommodates the source catheter 100. When theinner and outer sleeves 401 and 403 are assembled, they comprise thesource guide 400 shown in FIG. 4 c. Windows 402 and 404 may bepositioned rotationally and axially to create a clear window 405 ofarbitrary size for desired radiation emission as shown in FIG. 4 c. Thiscomposite window 405 may then be directed toward the tissue to beirradiated. The relative positions of sleeves 401 and 403 may be fixedby a tapered thread and nut similar to that shown in FIG. 2, as may theinner sleeve 403 in relation to the source catheter body 100.Positioning and movement of the source catheter and of the source guidesleeves 401 and 403 can be controlled by a program driven machine. Withthis source guide, stray radiation is eliminated, protecting healthytissue or tissue especially susceptible to radiation damage, such as thebowel. Such a source guide may be fashioned from barium loadedengineering plastic. Note that intermediate elements between the sourcecatheter and the shaft may necessitate additional seals to preventinflation fluid leaks, depending on the nature of the inflation port.

Directionality and control of the position at which radiation isdirected can be achieved in other ways. For example, the x-ray 101source within the catheter 100 can simply be shielded by a radio opaqueshield or coating on the x-ray tube or surrounding catheter, allowingradiation to be emitted only in a single cone or shaft, and the axialposition and rotational orientation of the catheter can be manipulatedin a selected pattern of movement so as to place the proper dose at eachregion of the tissue.

FIG. 5 depicts an embodiment of an applicator 505 in which a baseportion 506 of the applicator terminates near the proximal end of theballoon 300, and a cupped, separate element or bearing 500 is affixed tothe distal extreme of the balloon 300, for example by bonding. A shaftor source guide 501 has a branch 502 forming a curved guide lumen,closed at its distal end, and an axial extension 503 to cooperate withthe cup 500 to maintain the position of the shaft or source guide 501relative to the distal end of the balloon. If necessary to maintainaxial position of the cup 500 relative to wand guide 501, a groove 504(shown in alternate detail, FIG. 5 a) can be provided in the axialextension 503 into which the rim of the cup 500 can be heat formed afterassembly of the shaft 501 into the base member 506. The guide 501 can berotated within the shaft 200 such that the branch describes a circlewithin the balloon 300, directing radiation outward in a conical orradial manner, when the source catheter is in the branch. Such aconstruction would be useful in directing axial radiation into thefornices of the vagina, or for irradiation of such tissue alongside thesite of hysterectomy.

FIG. 5 b shows another embodiment wherein the shaft 501 is not rotatablebut has two branches 502 and 507 into which the source can be placed.Here the end of the shaft 501 a is fixed to the balloon. This forkedshaft 501 a can have the two branches or forks 502 and 507 at 180° or atany other selected angle, to protect, for example, the bladder and bowelby providing selected directional radiation. The source catheter (notshown) can have a slight bend near its tip so it can be steered into onechannel (502, 507), then the other.

The applicator embodiment 607 of FIGS. 6 a and 6 b comprises an optionalvacuum channel to evacuate exudate or other fluids from the region nearthe distal end of the balloon 300 through a port 605 in response tovacuum drawn on a port 606 at the proximal end of a multiple-lumen shaft600. Exudate or fluid is drawn through an annular passage 604 betweenthe catheter 100 and the shaft 600's inner diameter. The ports 605 and606 communicate through this annulus. To provide inflation of theballoon, a lumen 601 is provided in the wall of the shaft 600,terminating at a port 603 within the balloon, and at inflation port 602near the proximal end of the shaft 600.

A preferred method of use of the invention apparatus is illustrated inFIG. 7. FIG. 7 shows in frontal coronal section the applicator 505 ofFIG. 5 in the vaginal space of the patient, positioned to treat earlystage cancer at the mouth of the cervix 700, the cancer being indicatedby shading near the distal end of the applicator. In use, the deflatedapplicator 505 is inserted into the vagina. The source catheter 100 isthen inserted into the applicator, and the balloon is inflated,anchoring the applicator in position in the vagina. The controller andpower supply (not shown) are connected to the source catheter 100 (alsonot shown), and switched on. Then treatment proceeds. After treatment isconcluded, the system is switched off, the balloon deflated, and theapplicator removed.

The treatment plan is prescribed by the physician prior to applicationof radiation. If therapy is to be x-ray in nature, the plan may comprisespecification of dose intensity, penetration and dwell of the radiationsource by position from which radiation will be emitted and thedirection of emission or shielding utilized to protect healthy anatomy.Therapy may also include verification of dose delivered and feedbackfrom sensors placed near the anatomy being treated, as noted above, onor in the applicator, or on external anatomy of the patient or atinterstitial positions. Preparation of a plan of this sort andsubsequent treatment to plan are discussed thoroughly in copendingapplication Ser. No. 10/464,140, filed Jun. 18, 2003.

A further illustration of the use of apparatus of the invention is shownin FIGS. 8 a and 8 b. FIG. 8 a is a frontal coronal section through thevagina showing later stage cancer with involvement of the uterus andpelvic structure to the patient's left of the vagina. FIG. 8 b shows asagittal section of the anatomy to be treated. The inflated, curvedapplicator 208 b of FIG. 3 is shown positioned in the vagina, and partlyinto the uterus. In use, the cervix is dilated and the applicator isproperly positioned. The source catheter is then inserted and theballoon 300 inflated to abut the tissue and substantially fill the spacearound the radiation source, anchoring the applicator. The controllerand power supply (not shown) are connected to the source catheter 100,and switched on. Then treatment proceeds. After treatment is concluded,the system is switched off, the balloon deflated, and the applicatorremoved.

Another embodiment of the applicator of the invention, not illustrated,can have a balloon with a generally elliptical cross section, shortfront-to-back and shielded at front and back ends to protect the boweland bladder, which are indicated at 801 and 802 in FIG. 8 b.

The above described preferred embodiments are intended to illustrate theprinciples of the invention, but not to limit its scope. Otherembodiments and variations to these preferred embodiments will beapparent to those skilled in the art and may be made without departingfrom the spirit and scope of the invention as defined in the followingclaims.

1. An applicator for delivering ionizing radiation for intracavitybrachytherapy of the vagina and proximity, comprising: an inflatableballoon, with a shaft that extends into the interior of the balloon, theshaft having a conduit for inflating the balloon by admitting fluid tothe interior of the balloon, the shaft also being capable of receiving asource of ionizing radiation for delivery of radiation, and the shaftbeing rotatable relative to the balloon substantially without loss offluid from the interior of the balloon, whereby the balloon on the shaftcan be placed in a vaginal cavity with the balloon deflated, theninflated when in place, and with the ionizing radiation source in theshaft, the shaft can be rotated by manipulation of the shaft fromexterior of the vaginal cavity to control locations at which theradiation is directed. 2-4. (canceled)
 5. The applicator of claim 1,further including a means for adjusting length of an inflated portion ofthe balloon. 6-7. (canceled)
 8. The applicator of claim 1, wherein thesource of ionizing radiation comprises an electronic switchable x-raysource. 9-10. (canceled)
 11. The applicator of claim 1, wherein theballoon is formed of elastic material so as to generally conform totissue. 12-13. (canceled)
 14. An applicator for delivering ionizingradiation for intracavity brachytherapy of the vagina and proximity,comprising: an inflatable balloon, with a shaft that extends into theinterior of the balloon, the shaft having a conduit for inflating theballoon by admitting fluid to the interior of the balloon, the shaftalso being capable of receiving a source of ionizing radiation fordelivery of radiation, and adjustment means for adjusting the length ofan inflated portion of the balloon, whereby the balloon on the shaft canbe placed in a vaginal cavity with the balloon deflated, with adjustmentmade via the adjustment means, and, with the balloon inflated and theionizing radiation source in the shaft, the applicator can be used toirradiate a selected region of tissue.
 15. The applicator of claim 14,wherein the adjustment means comprises a slidable sheath that slidesaxially relative to the balloon for covering a desired length portion ofthe balloon from its proximal end so as to limit expansion of theballoon to a remainder portion not covered by the sheath. 16-17.(canceled)
 18. The applicator of claim 14, wherein the balloon is formedof elastic material so as to generally conform to tissue. 19-29.(canceled)
 30. An applicator for delivering ionizing radiation forintracavity brachytherapy of the vagina and proximity, comprising: aninflatable balloon, sized to fit to the vagina when inflated, with ashaft that extends into the interior of the balloon, the shaft having aninflation conduit for inflating the balloon by admitting fluid to theinterior of the balloon, and the shaft having a source conduit sized forreceiving an electronic, controllable source of ionizing radiation fordelivery of radiation to the region or proximity, whereby the balloon onthe shaft can be placed in a vaginal cavity with the balloon deflated,and, with the balloon inflated and an electronic radiation source in theshaft, the applicator can be used to irradiate a selected region oftissue. 31-33. (canceled)
 34. An applicator as in claim 30, wherein theballoon is generally cylindrically shaped, with a length greater than adiameter of the balloon. 35-42. (canceled)